Numerous power hand tools assisting a user in accomplishing a variety of tasks are known. Generally, such tools include a base and a tool head for performing a certain task, for example, cutting and/or sawing a workpiece composed of wood, plastic, metal or other various materials. Typically, a saw assembly includes a blade and various actuators adapted to displace the blade linearly along a longitudinal axis, rotate the blade about the longitudinal axis in various angled or beveled positions, and/or displace the blade along a pivot axis extending perpendicular to the longitudinal axis.
Examples of such a saw assembly include compound miter/chop saws allowing the user to selectively move the saw blade into any of a number of positions for square cutting, miter cutting, bevel cutting, or compound miter cutting where a combination miter angle and bevel angle are cut. In addition, it is essential that the saw blade move linearly to accommodate different lengths of the workpiece. In order to allow for the adjustment of the miter and the bevel angle, the saw blade, cutter or other working device can move along a horizontal base across the workpiece. Subsequently, if an angular adjustment of these elements is desirable, the bevel adjustment allows the saw blade, cutter or other working device to be positioned at an angle with respect to the horizontal base. At times it may be desired to cut a combination miter angle and bevel angle by simultaneously adjusting the angle of the blade with respect to both the horizontal base and a vertical guard.
Once the saw blade, cutter or other working device has been adjusted to the desired position with respect to the horizontal base and the vertical fence, locking mechanisms for the miter and bevel adjustment must be activated in order to prohibit movement of the saw blade, cutter or other working device from the set position with respect to the base and fence while the cutting operation is performed. These locking mechanisms need to be easily activated, adjustable and quick acting in order to optimize the efficiency of the cutting apparatus and provide convenience to the operator of the apparatus.
A typical saw assembly of the type, as discussed above, is disclosed in U.S. Pat. Nos. 6,035,754; 5,907,987; 5,870,938; and 5,870,838. As shown in FIG. 1, sliding compound miter saw 10 disclosed in the above-mentioned patents includes a base 12, a table 14, a housing 16, a saw blade 18, a blade guard 20, a motor 22 drivingly connected to saw blade 18, a handle 24 and a guard 26. The table assembly 14 is secured to the base 12 such that it can be rotated in order to provide adjustment for miter cutting. The housing 16 is secured to the table 14 such that it can be pivoted to adjust the angle of the saw blade 18 relative to table 14 for bevel cutting. To provide linear movement of a saw head consisting of the saw blade 18, the motor 22, the handle 24 and the blade guard 20 relative the table 14, the housing 16 has two support arms 34 coupled with the saw for synchronous sliding movement. The sliding movement of support arms 34 drives the housing 16 and the saw blade 18 so that the saw blade can be pulled through the workpiece when the size of the workpiece exceeds the cutting width of the saw blade 18.
A fairly complicated combination of movements can be inconvenient for the user operating the miter saw 10. First, displacement of support arms 34 attached to the saw head for synchronous linear displacement therewith to an initial position, in which the saw blade 18 is located next to the guard 26, increases the overall size of the saw. A portable tool design, like the miter/chop saw discussed here, requires that such a tool be compact.
Still another disadvantage of the above-disclosed miter saw may be observed during angular displacement of the saw blade between numerous angular positions which may be accompanied by undesired rotation of the saw head relative to the support arms. To minimize undesired rotation, many prior-art references including those discussed above disclose a two-arm support and guide system. Arms 34 can be positioned relative to one another either in a vertical or a horizontal plane.
The vertical arrangement of the arms, as disclosed in the cited patents, minimizes undesired rotation of a saw head until the saw head reaches a 40-45° angular position. In this position, the upper arm supports some of the load of the saw head and rubs against a plain bushing supporting this arm, which, in turn, causes drag. In the horizontal arrangement, both arms always support the load of the saw head and, thus, the drag problem manifests itself at an angle smaller than a 45° angle.
It is, therefore, desirable to provide a compact, light and simple structure saw assembly of the type described above. Also, the saw assembly having a structure with minimized play between a saw head, which includes the saw blade, its housing and other parts fixed to the blade for synchronous angular displacement therewith, and a support and guide system is also desirable.